1. Technical Field
The invention relates to clamping means and more particularly to the clamping means adapted to affix a resilient elastomeric sleeve member to a relatively rigid piston member or end cap of an air spring. Specifically, the invention relates to a clamp ring assembly employing a clamping ring having at least a pair of recesses on the inner diameter thereof which coact with a corresponding member of projections on the outer diameter of the piston member or end cap to positionally locate the clamping ring on the piston member and to effectively seal the open end of the elastomeric sleeve therebetween.
2. Background Information
Pneumatic springs commonly referred to as air springs, have been used for many applications, including motor vehicles, for a number of years to provide cushioning between moveable parts of the vehicle, primarily to absorb shock loads impressed on the vehicle axles by the wheels striking an object in the road or falling into a depression. The air spring usually consists of a flexible rubber sleeve or bellows containing a supply of compressible fluid and has one or more pistons movable with respect to the flexible sleeve. The piston causes compression and expansion of the fluid within the sleeve as the sleeve compresses and expands as the vehicle experiences the road shock. The spring sleeve is formed of a flexible elastomeric material containing reinforcing cords, and permits the piston to move axially with respect to another piston or end cap secured within open ends of the sleeve.
The open ends of the sleeves are sealingly connected to the piston and/or opposite end cap, and the integrity of this connection is always one of the important and major aspects in producing an efficient and maintenance free air spring. Another problem with existing air springs, and in particular, the clamp ring therefore, is that the clamp ring will move in its clamped position under dynamic air spring conditions causing movement of the clamped elastomeric material therebetween tending to loosen the sealing engagement and deteriorating the clamp integrity and causing ultimate air spring leakage and failure. This ring movement is especially critical during the jounce or collapsing stroke.
Another problem with existing air springs and the clamping of the elastomeric sleeve ends to the piston member and/or end cap is to secure a sufficiently tight seal to be able to withstand high fluid pressures contained in the fluid chamber without premature leakage or bursting even upon experiencing severe air spring movement and being exposed to the harsh environments on the undercarriage of a vehicle.
Some examples of air springs and band sealing devices are shown in the following patents described below:
U.S. Pat. No. 3,788,628 discloses a pneumatic spring-type system which includes a structure for anchoring the inner ends of a flexible rolling sleeve. The sleeve is positioned between surfaces characterized by having a saw-toothed shape with a circumferential groove and rib on an inner circumferential surface and two ribs on an outer circumferential surface. The opposite sides of the grooves converge at predefined angles with predetermined and matching radius of curvatures, the combination of which provides a gripping action to hold the flexible sleeve firmly in place by means of the saw-tooth design, in cooperation with the matching recess of the ring and sleeve flange.
U.S. Pat. No. 3,870,286 shows a fluid spring wherein the ends of the rolling sleeve are secured by annular clamping rings which engage against the internal surface of the sleeve. The clamping ring secures the rolling sleeve to the working cylinder. The clamping ring contains an annular groove deformation by which the rolling sleeve is held in place by virtue of this interacting groove-shaped design in combination with the clamping force exerted by the ring.
U.S. Pat. No. 4,489,474 relates to means for connecting a tubular flexible member to a piston which includes a recess near the piston end to which is secured a flexible member. The flexible member is wrapped over and around a ring-shaped fitting which secures the flexible member to the piston. The piston comprises a circumferentially extending recess adjacent to its end with the flexible sleeve being positioned and substantially filling the recess of the piston. The ring-shaped fitting is a conventional swaged ring and the end portion of the flexible member is trimmed from the portion extending from the piston ring with the flexible member substantially filling the recess of the shoulder of the piston. The piston employs a serrated edge to assist in griping of the flexible member.
U.S. Pat. No. 4,573,692 discloses an assembly for sealing two members, one of which has a cylindrical surface which supports the seal, wherein a sealing lip is provided to bear against the second member. A cylindrical surface supports the seal which comprises a hollow-cylindrical body having a lip which extends outwardly from the body with an elastomeric band circling the body to hold it firmly in place. The cylindrical surface contains a recess which extends circumferentially around the surface and receives a matching projecting element of the seal which extends from the inside diameter of the cylindrical body.
U.S. Pat. No. 4,629,170 shows a pneumatic spring with a pair of chambers formed by a pair of membranes that are sealingly attached to an axially spaced apart retainer and piston wherein the axial end of the membrane is compressed between a serrated surface of a solid member and a retaining ring. The ring is swaged, fitted or otherwise tightened to produce radial compression against the axial ends of the flexible membrane.
British Patent No. 199,789 discloses a metal securing band which grips a diaphragm and forces it against a tapered end portion of a tubular member.
U.S. Pat. No. 4,718,650 shows an air spring in which the ends of the flexible sleeves are connected to the sealing surfaces of a pair of axially spaced pistons by swaged or crimped clamping rings. The piston clamping surfaces are formed with serrations to assist the retention of the elastomeric material when forced therein by the clamping rings.
Other types of piston and end cap sealing arrangements for air springs are shown in U.S. Pat. Nos. 4,784,376; 4,787,607 and 4,787,606, all of which have been assigned to the Assignee of the present invention.
Another known prior art air spring construction includes a radially extending shoulder formed on the piston member on which the clamping ring seats and sealingly clamps the cut end of the flexible sleeve against a plurality of uniformly raised ribs formed on the axially extending sealing surface of the piston member adjacent the annular shoulder. However, such construction presents problems in that the clamp ring is not positively positioned on the annular shoulder, and is free to move in an upward axial direction upon the air spring experiencing severe jounce or extended positioning.
Many of the problems discussed above are solved by the clamping arrangement shown in U.S. Pat. Nos. 4,899,995 and 4,852,861. These patents show the use of a clamp ring having a single centrally located recess which aligns with an outwardly extending projection formed on the sealing surface of the piston and end member in order to position the clamping ring on the piston or end member. A pair of pinch areas are formed on opposite sides of the projection by outwardly extending annular rings or surfaces on the sealing surfaces of the piston and/or end member. These rings form the pinch areas or zones in cooperation with the axially extending inner annular surface of the clamp ring on opposite sides of the concave recess. Although this clamp ring assembly does solve many of the problems discussed above and is extremely efficient for many applications, it has been found that for certain air spring applications, especially for larger air springs having high internal pressure, it may not provide the necessary clamping power.
Therefore, the need exists for a still further improved clamp ring assembly for air springs which provides increased clamping and sealing for the open ends of the elastomeric member between the clamp ring and end member and/or piston.